Sunscreen may be big business, with sales topping $1 billion last year, but not nearly enough of us seem to buy into its importance, says Consumer Reports. More than half of the respondents in a new Consumer Reports survey say they usually skip sunscreen.

It’s not surprising, then, that the incidence of nonmelanoma skin cancers, the most common types, has reached alarming proportions — up 77 percent in the past 14 years — and rates of melanoma, the most deadly form of skin cancer, have also increased. Knowing the facts can save your birthday suit — and possibly your life.

1. You’re never too old to start wearing sunscreen. By age 40, you’ve racked up only half of your lifetime dose of UV rays; by age 60, just 74 percent. And for those older than 50, being in the sun sans protection can be particularly dangerous.

2. Covering up should be your first priority. Research shows that people who rely on sunscreens alone tend to burn more than those who stay in the shade and wear long sleeves. “Sunscreens are just one tool,” Wang says. Avoid the sun or stay in the shade when the sun is the strongest (10 a.m. to 4 p.m.), and dress right for the occasion. Wear a hat and clothing that’s made from tightly woven fabric.

3. Sunscreen can give you a false sense of security. It’s a common misconception that if you’re wearing sunscreen, you can stay in the sun for as long as you like.

4. A little dab won’t do ya. You should apply about 2 tablespoons for face and body. In Consumer Reports’ tests of sunscreens, its lab determined that applying half of that amount means you get about half of a product’s SPF (sun protection factor). But you can’t just slather it on once in the morning and think you’re done. It’s important to reapply every two hours when you’re out in the sun; even very high-SPF sunscreens lose their effectiveness after that.

5. There are sunscreen safety rules. The sunscreens in sprays can protect your skin as well as lotions. But they aren’t right for everyone. Sprays are flammable, so you shouldn’t use them if you’ll be near an open flame, such as a grill. The product can be inhaled, so don’t apply it directly to your face; spray into your hand, then rub in the sunscreen. Because of those concerns, Consumer Reports recommends not using sprays on kids.